As a conventionally known, active vibration isolation control system, JP2003-113892A (Reference 1) discloses a method of controlling a vibrator attached at an engine mount. To be more precise, in this disclosed method, a crank pulse sensor, which is equipped at an engine as a vibration-producing source, detects a crank pulse output with a rotation of a crankshaft of the engine. Driving torque from the engine is calculated on the basis of the crank pulse output detected by the crank pulse sensor. The calculation of the driving torque from the engine involves obtaining amplitude of vibration emanating from the engine. When the extent of the amplitude is inferior to a set amplitude value, operation of the vibrator attached at the engine mount is controlled on the basis of the amplitude obtained as described above and a predetermined phase. On the other hand, when the extent of the amplitude is, equal to, or greater than, the set amplitude value, phase of the vibration emanating from the engine is calculated on the basis of phase in an event that the engine torque reaches the maximum level. The operation of the vibrator is then controlled on the basis of the amplitude obtained as described above and the phase calculated as described above.
JP2003-195950A (Reference 2) and JP2003-202902A (Reference 3) respectively disclose method of performing a so-called adaptive control by active vibration isolation control systems. As algorithms for the adaptive control, these methods respectively employ an adaptive Lean-Mean-Square filter (hereinafter, referred to a Filter-XLMS) and a Delayed-X Harmonics Synthesizer Least-Mean-Square filter (hereinafter, referred to as DXHS LMS). In order to implement the adaptive control, the system disclosed in each Reference 2 and 3 incorporates the Filter-XLMS or the DXHS LMS, and an adaptive filter. Each of the Filter-XLMS and the DXHS LMS serves for obtaining coefficients, each of which modifies or compensates for amplitude and phase, while the adaptive filter serves for modifying or compensating for the amplitude and phase. Accordingly, control data for isolating vibration can be generated. Therefore, as described above, these methods of performing the adaptive control can be implemented preferably commensurate with an actual condition of a controlled object with high adjustability.
Being different from the adaptive control described above, JP11 (1999)-259147A (Reference 4) discloses a method of performing a map control by an active vibration isolation control system. In this conventional map control, control maps (data maps) have been prepared, control maps which store control data whereby a preferable control condition can be secured in response to a vehicle driving condition. The active vibration isolation control system reads a control data which is adequate to an actual vehicle driving condition at the time, and sends the control data to a vibrator. This map control can be carried out with superior responsibility.
According to any of the conventional methods disclosed in the above four references, a single control method is employed irrespective of a vehicle driving condition, i.e., irrespective of an engine rotational speed.
Points to be improved relevant to the method disclosed in Reference 1
In Reference 1, two types of control methods are selectively switched: the first control method whereby the operation of the vibrator is controlled on the basis of the phase of the engine vibration, the phase which is estimated by the engine crank pulse; and the second control method whereby the operation of the vibrator is controlled on the basis of the predetermined phase. In such circumstances, at an event that there is a difference or error between the estimated value (amplitude, phase) and actual value (amplitude, phase), or there is a difference or error between the predetermined value (amplitude, phase) and the actual value (amplitude, phase), preferable vibration isolation performance cannot be always exerted.
As far as vehicle vibration is concerned, at a time that the engine has been idly activated at a relatively low engine rotational speed, vibration apart from the engine rotation is so minor as to be insignificant. In such circumstances, the vehicle driver or occupant may be, on occasions, directly and strongly subjected to the vibration due to the engine rotation, whereby further improvements may be given preferably in a driving feeling that the vehicle driver or occupant may have. On the other hand, at a time that the engine has been activated at a relatively high engine rotational speed, various types of vehicle driving conditions may influence on the level of vibration that the vehicle driver or occupant may be subjected to. In such circumstances, requirements may lead to an active vibration isolation control with improved adjustability.
Points to be Improved Relevant to the Method Disclosed in References 2 and 3
In order to perform the adaptive control, the active vibration isolation control system monitors, as appropriate, a condition of the controlled object, and generate control data to be adequate to an actual condition. The vibrator is operated in response to the control data. In such circumstances, responsibility of the adaptive control may not be attained to a sufficient level. For example, at a time that the engine has been idly activated at a relatively low engine rotational speed, vibration to be transmitted to the vehicle driver or occupant may not be, on occasions, isolated at a sufficient level.
Points to be Improved Relevant to the Method Disclosed in Reference 4
In order to perform the map control, the predetermined control maps are employed. In such case, the number of control maps, which the system can store, is limited. Therefore, the map control may not be, on occasions, performed with a sufficient adjustability, especially in an event that many elements, which produce vibration, should be considered for the purpose of obtaining a vehicle driving condition. Moreover, when the system is subjected to an influence of temperature changes at the large extent, such as when an engine unit has not been warmed up yet, it may be, on occasions, difficult for the predetermined control maps to be adjusted in response to the changes of influence amount. Likewise, when a vibration transfer function has changed across the ages, it may be, on occasions, difficult for the predetermined control maps to be adjusted in response to the changes of influence amount.
The present invention has been made in view of the above circumstances, and provides a method of setting control data capable of preferably attaining an active vibration isolation control from a time when an engine is activated idly to a time when a vehicle drives at a relatively high engine rotational speed, whereby a driver or occupant does not have much discomfort. More over, the present invention provides a control method of controlling the same.